A variety of wireless chargers is commonly used to charge electronic devices, for example user devices such as smartphones, tablet computers, “2 in 1” mobile computing devices, or wearable devices. Wireless chargers typically include induction chargers, which use an induction coil (sender (Tx) coil) to create an alternating electromagnetic field. A mating induction coil in the user device (receiver (Rx) coil) takes power from the electromagnetic field and converts it back into electrical current to charge the battery of the user device. The two induction coils in proximity may combine to form an electrical transformer. Greater distances between sender and receiver coils may be achieved when the inductive charging system uses resonant inductive coupling.
Parameters of electromagnetic fields created by wireless chargers may be subject to certain requirements in order to conform to interoperability standards and acceptable levels of user exposure. For example, international organizations such as Alliance for Wireless Power (A4WP) and Wireless Power Consortium (WPC), among others, define requirements for interoperability such as the frequency of operation, magnitude of fields, and power levels in wireless power systems. Regulatory bodies, such as the U.S. Federal Communications Commission (FCC) and International Commission on Non-Ionizing Radiation (ICNIRP), provide regulatory requirements for human exposure to radio frequency (RF) waves and electromagnetic radiation.
Current solutions may include wireless chargers with coils designed such that the power transfer may conform to the power levels defined by the wireless power (i.e. A4WP and WPC) standards, while also meeting the regulatory limits imposed by the FCC and others.